Out-of-autoclave molding of carbon fiber composites pipes with interlaminar carbon nanotubes

Carbon fiber reinforced (CFR) composite rings with and without interlaminar carbon nanotubes (I-CNTs) were manufactured starting from high performance prepregs used in aeronautics. Nano-particles deposition was obtained by an innovative easily scalable procedure which does not affect composite processability. A CNTs-solvent solution was sonicated for an established time to reduce bulk CNTs agglomerates. The solution was poured on prepreg stripes and left at room temperature for solvent evacuation. The prepreg stripes were wrapped on steel pipe to obtain the annular configuration and manufactured by an out-of-autoclave (OOA) process. The consolidation pressure was applied through a thermo-shrinkable tube and curing occurred in oven. Stereomicroscopy and mechanical tests were performed on CFR and I-CNTs/CFR rings. A good adhesion among the plies was observed as well as the positive effects of CNTs deposition; an increase of 34%, 15% and 17% was obtained for the stiffness, the peak load and the fracture energy of the functionalized rings, respectively.